A circulating, submerged organ culture technique in which partially dissected embryonic mouse heads can be cultured to study palatal development has been refined. The effects of removing the tongue, the brain, the tongue and brain, and the tongue, brain and mandible have been studied. The goals for the coming year are to characterize the events occurring during the in vitro development of the palate in embryonic preparations with the tongue and brain removed and to compare these events with the in vivo situation. Synthesis of DNA, RNA and sulfated mucopolysaccharides will be followed in cultured preparations by isotopic labelling and autoradiography. Agents with known effects on cellular activities, e.g. colchicine, actinomycin D,B-aminoproprionitrile, etc., will be used to define the occurrence and timing of specific cellular activities necessary for palatal closure. The effectiveness of the inhibitors will be monitored by the simultaneous addition of appropriate isotopically labeled compounds to the medium. Morphological changes will be correlated with altered cellular activities.